In prior-art diverting pulleys the axle of the diverting pulley is locked into position with a locking plate that extends into a groove made in the axle. The groove is milled into the axle from the transverse direction, in which case the groove comprises a detent surface facing the transverse direction of the axle, against which the locking plate is placed.
A problem in these prior-art solutions is that since the groove is milled in the solutions at a distance from the butt end of the axle, the detent surface that is against the locking plate remains hidden behind the butt end of the axle. That being the case, it is not possible to visually inspect the contact point of the locking plate and the detent surface of the axle. Inspecting this point is necessary so that the condition of the locking plate, and indirectly also the condition of the bearings, can be determined.
If servicing intervals are long, the condition of bearings can deteriorate over time so that a diverting pulley rotating on an axle starts essentially to try to rotate the axle. When the axle tries to rotate, the pressure exerted on the locking plate by the detent surface and also the wear resulting from to-and-from loading increase. Verifying the condition of the locking plate is laborious in prior art, because the diverting pulley structure has to be opened for this purpose.
The condition of the bearing of the diverting pulley moving along with the counterweight of the elevator is almost impossible to estimate in advance and therefore the probable failure time of the bearing is undeterminable. Only minor noise, heat and vibration results from a bearing failure, so that noise, heat or vibration are not suited as a cost-effective indicator of a bearing defect.
The chief maintenance function for the bearing of a diverting pulley of a counterweight of an elevator is visual and observations in the elevator hoistway based on sound. Failure of a bearing of a diverting pulley of a counterweight of an elevator might result in structural damage in the counterweight, freefall of the counterweight and gripping of the elevator car.